Taxonomy

Elodea nuttallii | Nuttall's Waterweed | Tím uisce chaol

Distribution

Status

Conservation status

Not Assessed

Legal status

Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).

Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).

Regulated invasive  species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].

First reported in the wild

1974

Invasiveness

Invasive species - risk of High Impact

Irish status

Established

Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Ornamental purpose

Invasive score

19

NAPRA Ireland risk assessed

Yes. This species underwent a  Non-native species APplication based Risk Analysis  in 2014.

Overall risk of this species to Ireland is categorised as: MAJOR with a VERY HIGH level of confidence.

Overall conclusion summary:  This non-native species continues to pose a major risk to native biodiversity, native ecosystems and conservation goals as well as having the potential to cause negative socio-economic impacts in slow-flowing or still waters due to its capacity to spread rapidly and establish dense infestations. 

 View the full risk assessment: http://nonnativespecies.ie/wp-content/uploads/2014/03/Elodea-nuttallii-Nuttalls-Pondweed1.pdf

Species Biology

Identification

Submerged, aquatic plant, anchored in the substrate. Stems long, branched and up to 3m long, leaves minutely serrated and in whorls of 3-4, leaves narrower and more acute than E. candensis (Stace, 1997).

Ecology

Elodea nuttalli may follow the same pattern of colonisation, rapid expansion and decline and naturalisation as its conspecific Elodea candensis, (Simberloff & Gibbons, 2004; Simpson, 1984), though this pattern was in part due to E. nuttalli displacing E. canadensis (Simpson, 1984). E. nuttalli changes the composition of freshwater systems by shifting the systems towards a more macrophyte (aquatic plants large enough to be seen with the naked eye) dominated community, by increasing the cover of floating plants (Kelly et al., 2015). E. nuttalli has lower richness of algal periphyton (a mixture of algal, cyanobacteria and small plants that grow on larger plants and algae), and changes the composition of the macroinvertebrate community, though not the species richness or abundance (Kelly et al., 2015). A key concern is the negative correlation between E. nuttalli cover and that of charophytes as many of the species are rare or endangered (Kelly et al., 2015).

Habitat

Inland surface waters; Estuaries

Reproduction

All reproduction in Elodea spp in the British Isles is through vegetative means, as only female plants are present (Simpson. 1984).

Pathway and vector description

Elodea nuttallii is sold as an oxygenator/ornamental weed and kept in artificial watercourses, garden ponds and aquaria, from where it is introduced into the wild, either accidentally through flooding or waterfowl or deliberately by dumping of plant material into water courses (Millane & Caffrey, 2014).

Mechanism of impact

Competition, Bio-fouling

Management approach

There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017).

Manual

Hand-picking is the most effective method for small infestations (<1m²) provided all rhizoids are removed (CAISIE, 2013).

Mechanical

For large areas (>1000m²) best practice for control is to use cutting boats in conjunction with a containment net to capture any floating fragments (CAISIE, 2013). Newman and Duenas (2010) recommend this work should be carried out before July.

Environmental

Benthic barriers (jute mats) can be used for control of infestations from 1 – 1000m² (CAISIE, 2013). Using jute mats rather than plastic sheeting has the advantage of allowing the germination of the seeds of native plant species (Caffrey, 2010). For stands in shallower water (<1m) a double layer of matting is more effective (CAISIE, 2013).

The use of dyes can be successful in static waters provided they are applied before the plant starts to grow in the Spring (Newman & Duenas, 2010).

Monitoring

For control of E. nuttallii best practice is at least annual monitoring of sites for regrowth (CAISIE, 2013).

Broad environment

Freshwater

Habitat description

Lakes, rivers, canals & other slow moving waterbodies.

Species group

Plant

Native region

North America

Distribution

World distribution(GBIF)

Irish distribution

Established - Widespread. Locally abundant, forming thick mats (Millane & Caffrey, 2014). Displaced Elodea canadensis in parts of its range (Simpson, 1984) and may be undertaking a similar pattern of invasion (colonisation, rapid expansion, decline), though this remains to be seen.

Native distribution

Native to North America.

Temporal change

Date of first record category

1971-1980

Fifty year date category

1951-2000

Records submitted to Data Centre in 2017

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre. Do not purchase or plant in your garden. Dispose of garden waste and nuisance plants responsibly.

References

Publications

Caffrey, JM et al. (2010). A novel approach to aquatic weed control and habitat restoration using biodegradable jute matting. Aquatic Invasions, 5 (2), pp. 123-129. http://www.aquaticinvasions.net/2010/AI_2010_5_2_Caffrey_etal.pdf Site accessed 4 August 2017.

Control of Aquatic Invasive Species and Restoration of Natural Communities in Ireland (CAISIE). (2013). Best practice control measures for Nuttall's pondweed Elodea Nuttallii. EU LIFE+ Project NAT IRL 000341. http://www.fisheriesireland.ie/invasive-species-1/368-best-practice-control-measures-for-nuttalls-pondweed-1/file Site accessed 24 August 2017.

European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.

Millane, M. & Caffrey, J. (2014). Risk Assessment of Elodea nuttalli (Planch.) St John – Nuttall’s Pondweed. Prepared for Inland Fisheries Ireland and the National Biodiversity Data Centre.

Newman, JR and Duenas, MA (2010) Information Sheet 25: Elodea nuttallii, Nuttall’s pondweed. Centre for Ecology and Hydrology. Natural Environment Research Council. Wallingford. http://nora.nerc.ac.uk/10425/2/N010425_leaflet.pdf Site accessed 24 August 2017.

Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin.

Simberloff, D., & Gibbons, L. (2004). Now you see them, now you don't!–population crashes of established introduced species. Biological Invasions, 6(2), 161-172.

Simpson, D. A. (1984). A short history of the introduction and spread of Elodea Michx in the British Isles. Watsonia, 15(1), 1-9.

Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge.

Inland Fisheries Ireland

CABI Datasheet

Images